Once upon a time there were giant reptiles called dinosaurs. They were really big. They lived 165 million years ago. Probably a couple years after. Some dinosaurs like Triceratops had very flat teeth like ours. Others, such as Allosaurus had big sharp teeth like lions. The largest was Argentinosaurus. We saw it's fossil in a museum in Georgia. I think the cause of dinosaurs extinction was that a meteor hit and the dust blocked out the sun.